A scanner has plasma loop or plasma window antennas for selectively scanning for ID tags along distinct radials of the scanner. The housing having a recess, a first cantilever spring, a second cantilever spring. The animal litter is in the form of discrete plural particles which tend to agglomerate when wetted. The resilient pawl plates are compressed within the large diameter wall section, and frictionally contact an inner surface of the large diameter wall section. The CPU frequency regulating circuit detects the load voltage of the power circuit of the CPU for selecting an appropriate frequency to the CPU according to a working condition.